The Program Project that this Bioanalytical Core Proposal is part of intends to develop new opioid analgesic drugs that will replace existing narcotics. It is anticipated that these new drugs will be as effective as existing opiate drugs but will be safer and have less abuse potential. The Bioanalytical Core Proposal provides essential analytical services to other parts of the associated Program Project responsible for the development of new opioid peptide and peptide-like compounds. These services include measurements of binding afinity at the different opioid receptor types, measurements of potency using isolated tissue assays, determination stability against degradation by tissue, studies of the ability of these compounds to pass membrane barriers and analgestic activity after direct injection into the brain and after systemic injection. The basic information on opioid receptor binding affinity and potency will be obtained for all compounds under development. Compounds selected from these studies will be further tested using the other three approaches. Stability, membrane permeation and analgesic activity studies will identify new compounds most likely to have clinical utility as new opioid drugs.